Massively-parallel access to the activity of large populations of individual neurons with high spatial and temporal resolution has been a long-sought goal in neuroscience. With advances in MEMS and microelectronics, there has been significant progress toward this goal as planar fabrication processes have been applied to realize chronic extracellular microelectrode arrays. Many previously reported neural probes use electrical signals to stimulate neurons. However, such electrical stimulation can damage neurons. Additionally, because the necessary electrical fields extend across large areas rather than individual neurons, such electrical stimulation can also suffer from poor spatial resolution. To address these problems, an optical stimulation method has been attempted with some success using an optical fiber attached to a probe shank as the optical source (S. Royer et al., “Recording and stimulation of single neurons in the hippocampus of the behaving rat,” Society for Neuroscience Annual Meeting, 2008). However, this hybrid structure makes the probe bulky because the size of the optical fiber is comparable to the size of the probe. Also, the hybrid structure is difficult to be accurately assembled and this structure makes it difficult to control the target stimulation position.